The present invention relates to a method for recording flow boundary layers in liquid media by photochemical means.
For recording flow patterns in a liquid flow medium, the use of an emulsified brushing medium of linseed oil varnish, Turkish-red oil and lamp black on a white background, with spotted dot or line application is known. However, substantial transfer or matter is not involved in this method. Rather, the method involves a mechanically effective indication of flow direction and intensity. With diffusing solids under water, it is possible to make boundary layer transition lines visible (J. D. Main-Smith, A.R.C. Technical Report R. & M. No. 2755, Feb. 1950, pp. 1-16). The velocities at the model corresponded to up to 101/2 knots=5.4 m/s for a ship 125 m long. S. K. Stynes & J. E. Myers worked with a solution of benzoic acid in water (A.I. Ch. E. Journel, vol. 10 (1964), No. 4, pgs. 437 to 444).
It is further known to utilize for the pictorial recording of liquid flows along solid surfaces, the precipitation of difficult-to-dissolve substances within a gelatinous layer in the flow liquid (U.S. Pat. No. 3,753,652). As suitable substances can be considered azo dyes, and ferri or ferro cyanides of copper or iron.
A method relating to the use of gaseous fluid (usually air) for making steady-state flow states visible by photochemical means utilizes ready-made photo gelatin containing silver bromide for displaying the boundary layer (U.S. Pat. No. 3,774,225). The method operates with photochemically reactive gases, especially with hydrogen sulfide, admixed to the air. The hydrogen sulfide diffuses into a swelled photo gelatin and produces a silver sufide image which is subsequently made visible by fixing.